Mount for circuit elements



Oct. 13, 1970 I I s s ETAL 3,534,309 ,MOUNT FOR CIRCUIT ELEMENTS I Original Filed Aug. 5, 1964 2 sheets sheec 1 /g,'/ 42 48 44 a5 44 '62 44 36 F i0 f Q 13 $0 Q fnz/enzans Cd. 13, 1970 o RENSKERS EIAL 3,534,309

MOUNT FOR CIRCUIT ELEMENTS Original File d'Aug. s. 1964 2 Sheets-Sheet 2 United States Patent 3,534,309 MOUNT FOR CIRCUIT ELEMENTS John O. Renskers, Crystal Lake, Charles S. Liebman, McHenry, Robert J. Salzman, Woodstock, and Charles E. Schroeder, Mundelein, Ill., assignors to Coilcraft, Inc., Cary, Ill., a corporation of Illinois Original application Aug. 3, 1964, Ser. No. 387,139, now Patent No. 3,368,276, dated Feb. 13, 1968. Divided and this application Mar. 6, 1967, Ser. No. 634,789

Int. Cl. H011? 15/02, 15/10 US. Cl. 336-65 7 Claims ABSTRACT OF THE DISCLOSURE A mounted coil or the mount therefor consisting of a rectangular piece of stiff insulating paper, having parallel stiff terminal wires along opposite edges thereof, the center portions of the wires being forced through the paper to attach them insecurely to the paper, and a coil engaged by tongues in an aperture in the paper between the terminal wires to attach it insecurely to the paper, the leads of the coil being soldered to one pair of ends of the terminal wires, and the whole of said assembly except for the other pair of terminal wire ends being encapsulated to provide ultimate permanence to the assembly.

CROSS REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 387,139, filed Aug. 3, 1964, now Pat. No. 3,368,276, by John O. Renskers et al., entitled Mount for Circuit Elements,

BACKGROUND OF THE INVENTION The present invention relates to a mount for electric and electronic circuit elements or, more narrowly, for coils and transformers and to coils, etc. so mounted for insertion into electronic and electric circuitry.

A mounted coil somewhat similar to the invention has been devised wherein staples are driven into the edge of a rectangular stiff paper board and the staple ends then splayed out to extend beyond the edges of the paper. A coil is glued to the face of the paper between the staples and the coil leads are wrapped around the staple ends projecting beyond one edge of the paper.

There are several difliculties with this construction. Since the attaching wires are inserted in a true stapling fashion, i.e., the wires are bent into a U-shape and the ends of the wires driven through the paper material, the wire ends must be equal and somewhat limited in length. That is, the legs of a paper staple to be inserted by ordinary stapling machinery must be the same length and they must be short enough so as to have the necessary rigidity so that a blow on the back side of the staple will punch the legs through the material in which they are to be inserted and not bend them. Likewise, gluing a coil to the face of the material between the staples is a time consuming and therefore an expensive operation. The glue must be applied, the coil deposited on the glued patch, and the assembly thereupon set aside to dry for a certain period of time. The gluing operation calls for a substantial number of steps, the drying time is expensive, and the glued construction is generally unsuited to automation.

SUMMARY OF THE INVENTION The coil form of the invention is directed to the improvement of this structure to avoid these disadvantages. The form of the invention requires no symmetry of terminal wire ends and imposes no limitations on the length thereof. It avoids a gluing operation for cementing the coil to the form. The form of the invention is highly ice versatile and capable of mounting many circuit components in different configurations to meet various purposes. Its adaptation to these various configurations is simple and easy.

Many materials may be employed in the construction of forms incorporating the invention and, with these different materials, the invention is capable of several embodiments, all of which, however, enjoy the same ad vantage as that described above, of unsymmetrical terminal wires, an indefinite length of terminal wires, accuracy of terminal wire location for purposes of automated circuit board insertion, and exceedingly low cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of a completed mounted coil illustrating one embodiment of the invention;

FIG. 2 is a section taken along the line 2-2 of FIG. 1, looking in the direction of the arrows;

FIG. 3 is a front elevation of a mounted coil illustrating another embodiment of the invention;

FIG. 4 is a section taken along the line 4-4 of FIG. 3 looking in the direction of the arrows;

FIG. 5 is a front elevation of another form of coil mount;

FIG. 6 is a plan view of the mount of FIG. 5 taken from the line 6-6 of FIG. 5, looking in the direction of the arrows;

FIG. 7 is a front elevation of another form of coil mount;

7 FIG. 8 is a side elevation of the mount of FIG. 7 taken from the left side thereof;

FIG. 9 is a section through an appropriate set of dies whereby the mount of FIG. 7 is formed showing a terminal wire in elevation on top of a mount board in section;

FIG. 10 is a view similar to FIG. 9 showing the first step in the formation of the mount;

FIG. 11 is a section along the line 11-11 of FIG. 10 showing the stage of operation of FIG. 10;

FIG. 12 is a view similar to FIG. 11 showing a second stage in the formation;

FIG. 13 is a view similar to FIG. 11 showing the concluding stage in the formation;

FIG. 14 is a front elevation of one form of mounting board adapted for the attachment of a coil thereto;

FIG. 15 is a similar view of the board of FIG. 14 showing a high inductance coil, partly in section, mounted thereto;

FIG 16 is a section taken along the line 16-16 of FIG. 15;

FIG. 17 is a view similar to FIG. 16 showing a low inductance coil mounted therein;

FIG. 18 is a front elevation of a mounting board adapted for the attachment of a medium inductance, universally Wound coil;

FIG. 19 is a section taken along the line 19-19 of FIG. 18 looking in the direction of the arrows showing a coil mounted therein;

FIG. 20 is a front elevation of a mounting board having an alternative form of coil attaching means;

FIGS. 21, 22 and 23 are sections taken along the line 21-21 of FIG. 20 showing optional ways of attaching coils to the board of FIG. 20;

FIG. 24 is a front elevation of a mounting board incorporating a third provision for coil retention;

FIG. 28 is a modified form of a mount adapted substantially for full enclosure of a coil or circuit element and, optionally, for six terminal connection;

FIG. 29 is a section through a mounted coil employing the mount of FIG. 28 and may be considered generally as being taken along the line 2929 of FIG. 28 looking in the direction of the arrows; and

FIG. 30 is a front elevation of a coil wherein the mounting board itself serves as a coil form.

DESCRIPTION OF THE PREFERRED EMBODIMENT As will be apparent from the drawings viewed collectively and referring particularly to FIG. 1, the mounted coil of the invention consists first of a generally square mounting board having two relatively stilt terminal wires 12 adjacent opposite edges of the board and extending beyond the board at one end 14 only a short distance and at the other end 16 a substantial distance. A material which we have used for the mounting board which meets our purposes excellently is an electrical grade vulcanized fibre known in the trade as fish paper. Such a material is sold under the trademark Armite, a mark of the Spaulding Fibre Company of Tonawanda, NY. This paper is a dense relatively stitt composition board. Other cardboard-like insulating materials may be employed however as long as they possess a certain minimum degree of stiffness.

A coil or other circuit element 18 is secured to the center of the mounting board. In the case of FIGS. 1, 3 and 17 this circuit element is a single layer coil 20* wound on a tubular form 22 which is pressed into a window 24 formed in the mounting board 10. The leads 26 of the coil are wrapped tightly around the short ends 14 of the terminal wires immediately above the mounting board, and the coil as thus mounted is dipped into a bath of a suitable protective coating 28 to protect and insulate the circuit element, to bind all parts firmly together and to impart rigidity to the mounted coil. Desirably the dip will be such as to immerse the mounting board totally but leave the lower long ends 16 of the terminal wires 12 uncoated. A phenol formaldehyde coating composition identified in the trade as Durez (a trademark of the Durez Plastics & Chemicals Co.) has been found to be highly satisfactory. The Durez comes as an uncured powder. A thick solution or suspension in alcohol or acetone is made, the mounted coils dipped and permitted to dry and then baked to cure the resin. The Durez forms a hard and strong coating over the entire mounting board, coil, and adjacent areas of the terminal wires, encapsulating the entire unit and fixing the relative positions of the various parts and making rigid the mounting board. It will be appreciated that, with the Durez encapsulation, the assemblage of the coils prior to dipping may be weak or fragile. Strength only sufficient to hold the members in place in the successive steps of wire insertion, coil mounting, coil lead connection, dipping, etc. and incidental handling is needed.

Although the Durez coating is shown only in FIGS. 1 and 2, it will be appreciated that it may be employed to obtain the several advantages in any of the modifications illustrated, and its omission from the illustrations of other modifications is simply to make clear the internal structure of the mounted coils.

As stated above, the method of inserting the terminal wires employed in the art has been by a conventional stapling step wherein the wire is bent into a U-shape and the free ends of the wire are then driven through the mounting board and the feet thereafter splayed out. This imposes two limitations; first, that the legs of the staple must be equal in length and second, that the legs of the staple cannot be long. It also imposes a limitation corollary to the second limitation that the mounting board material must be easily penetrated.

As an improvement over this construction we have devised the coil mount illustrated particularly in FIGS. 7 and 8 and a method of making it in FIGS. 9 through 13. In FIG. 7, we show a mounting board 30 as described above with terminal wires 32 attached thereto, short ends 34 projecting from one side of the board and long ends 36 beyond the opposite side. As in conventional stapling, the end portions 34 and 36 of the wires lie on one side of the board and a central portion or bight 38 lies on the other side of the board. The method which makes possible the disparity of terminal wire end lengths is the step of driving the bight of the terminal wire through the board to effect this relation rather than driving the ends of the terminal wire through the board.

In this construction the use of the fish paper or equivalent paper stock is highly desirable. It has stiffness and strength sufiicient to effect a good retention of the terminal wires. The mounting board may be slotted as at 40 for the reception of the wire bights or the central portion of the wire may be driven through the unslotted board material to break its own way. In either case the fish paper has sufficient resilience to snap back into plane after after the passage of the bight of the terminals wire therethrough and so elfect the desired retention of the terminal wire.

Illustrative mechanism is shown in FIGS. 9 through 13. In these figures we show upper and lower clamping members 42 and 44 which are adapted to engage substantially the entire surface of the mounting board aside from the line of operation involved in the terminal wire insertion. The upper clamping member is centrally vertically slotted for the reception of a tongue 46 about equal in thickness to the diameter of the terminal wire. The tongue is movable up and down relative to the upper clamping member. The upepr clamping member is likewise grooved at 48 on its bottom face in line with tongue 46 for the reception of a terminal wire.

The bottom clamp 44 likewise has a slot therein in alignment with and wider than the slot in the upper clamping member for the reception of a vertically reciprocable die member 50 somewhat wider than the tongue 46.

The mounting board 30 is placed on the lower clamping member and a terminal wire 32 placed thereon. The upper clamping member is then brought down to clamp securely the mounting board and retain the terminal wire in its proper position across the mounting board. Thereafter the tongue 46 is moved downward to drive the central portion or bight 38 of the terminal wire through the mounting board. As stated, the mounting board may be slotted for the passage of the wire bight or the bight may tear its own way through. In either case the configuration will be generally as shown in FIGS. 10 and 11. The tongue 46 is then retracted to permit the bent-down edges of the torn or preformed slot in the fish paper to return to a position near their orginal plane behind the bight 38 of the terminal wire as shown in FIG. 12. Thereafter the lower die 50 is raised to flatten the bight of the terminal wire against the under side of the slot in the fish paper.

Although we have illustrated the insertion of a single wire only, it will be evident that the mechanism of FIGS. 9-13 may be duplicated to insert both wires simultaneously or even further multiplied for the insertion of several wires, as withsome modification described below. Simultaneously with this operation, appropriate dies can be used to shape the exterior outline of the mounting board, to score the paper as desired, and to fashion windows therein as will be later described. Following completion, the upper clamping member 42 is raised to release the completed coil mount.

The mechanism described here is purely illustrative, but it is well suited to automatic and rapid operation. The fish paper may be supplied in strips and the terminal wires supplied from coils mounted transversely to the line of travel of the strips. The cutting to length of the ends of the terminal wires can likewise be performed simultaneously with the assembly procedure. Thus, the wire could be fed against a stop 49, and a shear 51 acting against an anvil 53 could move with the upper clamping member 42 to do the cutting.

A coil or circuit element will then be attached to the mounting board in a fashion to be described later, the leads thereof secured to the short ends 14 of the terminal wires, these ends soldered as by a dip, and the whole mounting board then immersed in Durez and cured to obtain a mounted coil like that of FIG. 1.

It will be appreciated that the attachment of the terminal wires to the mounting board is not inherently as secure as the attachment of the staple in the above described coil mount of the art. By deliberate effort the terminal wires can be pulled out from behind the slot edges 52. On the other hand the assembly is as strong as it need be. The retention of the terminal wires is ample to permit a wrapping of the coil leads thereabout without danger of displacement, and after the Durez dip and baking, the entire structure is cemented together into a unit which posses ample characteristics of strength.

This limited strength requirement imposed on the terminal wire and mounting board connection during the mounted coil assembly suggests other modes of attachment of the terminal wires to the mounting board. FIGS. 1 and 2 show another possible assembly technique. In this case the terminal wires 12 are fed transversely between two strips of appropriate paper 54 having tacky gummed surfaces which face each other. Thereafter in a simultaneous pressing and blanking operation the wire may be cut to length, the paper pressed so that the gummed surfaces thereof engage each other encompassing the wires, and such punching and shearing done as may be desired of the double paper layer. Thereafter the coil will be inserted, leads secured and the whole Du.reZ dipped as described before.

FIGS. 3 and 4 illustrate another modification of the coil mount wherein the terminal wires are adhesively secured to a single sheet of the fish paper. The paper may have a gummed side on which the terminal wires may be laid transversely of the strip. Again the wires may be cut, pressed into the gummed surface of the strip for firm connection and the paper shaped as desired. The rest of the assembly then follows in order. Such a procedure will serve well where the adhesive employed is a curable strong type such as epoxy or polyester. Polyester and epoxy adhesives however are expensive and require a separate operation and time for curing.

To permit the use of ordinary contact cements we have devised the mount illustrated in FIGS. 3 and 4. It should be appreciated that the bond of Durez to a sement coated surface is no stronger than the adhesion of the cement to that surface. Durez bonds much more strongly directly to the paper than to ordinary contact cements. Therefore in the modification of FIG. 3, rather than coating one entire side of the paper strip, we print lines 56 of contact cement where the terminal wires are to be placed and form windows 58 through the paper in the center of these lines, for instance, slightly wider than the wire. The terminal wires, as before, are deposited on the glued strips. In the operation of cutting them to length, the wires are dented down into the windows 58 as at 60. The glue retention will be suflicient to hold the terminal wires for the manipulations to be performed thereon in the course of assembling the mounted coil. Thereafter the Durez coating bonds the wires closely to bare paper surfaces. There will be leakage of Durez through the windows 58 and through the coil window 24 to bond the coatings of Durez on each side of the paper together and to encase the terminal wire dents. The Durez between the dents 60 and the window edges imposes manipulative loads thereon upon the paper of the window edges thereby preventing longitudinal shift of the Wires within the Durez casing, and the Durez between the dents and the sides of the windows 58 prevents rotational displacement of the terminal wires. It will be appreciated that this modification demands that the dents 60 extend only into and not through the windows 58, and the coil mount may thus have an absolutely flat side.

FIGS. 5 and 6 illustrate another method of temporary terminal wire attachment to a mounting board which has particular advantages of its own. In this modification We use a mounting board 10 of corrugated paper having the usual outer plies 63 and a corrugated middle ply 65 supporting and spacing the outer plies. The corrugations leave through-apertures 67 that snugly receive the terminal wires 12. We find the frictional engagement of the wires within the apertures normally sufiicient to resist manipulation. Where the handling is particularly vigorous, however, it may be advantageous to swage a flat 69 on the wires after their insertion to anchor them more securely. The cardboard restores itself substantially after the swaging.

The advantage of this structure is that the mounting board is fiat and that the terminal wires are spaced from the planes of either of the faces thereof. As a consequence, the entire face or faces of the board is available for coil mounting and coils of substantially greater diameter can be accommodated. This should be compared with the mount of FIGS. 7 and 8 where the coil is limited in diameter to the space between the bights 38 or to the diagonal distance between the inside of the short end 34 of one wire and the inside of the long end 36 of the other.

In FIG. 3 it should be noted that the short terminal wire ends 14 are pinched off rather than sharply sheared off so as to leave a flattened pointed tip 62. This tip provides a shearing edge for the relatively fine wire of the coil leads 26 so that the leads may be cut off after wrapping on the terminal wire without the necessity for picking up another tool. A detail such as this contributes greatly to speed of assembly.

It should be further noted that the tOp and bottom edges 71 and 73 of the boards are notched as at 75'. Both the short and long terminal wire ends are usually immersed in a solder bath, the short ends to solder the coil leads thereto and the long ends to tin them. Such dips present the possibility of charring the top and bottom edges of the boards and creating a conductive carbon path between the terminal Wires. The notches 75 interrupt the continuity of these edges.

The remaining figures all relate to various ways in which a circuit element such as a coil may be retained by the mounting board in preference to the simple glue attachment as described above. As indicated before the glued attachment has several disadvantages. First it is slow. Second, the strength of the Durez coating is reduced in that it is not bonded to the whole surface of the mounting board.

FIGS. 13 through 19 illustrate a first form of temporary coil attachment prior to the Durez dip. In all of these figures, the mounting board is shown without the terminal wires. It will be appreciated that the terminal wires may be attached in any of the fashions indicated in FIGS. 2, 3, 5, or 7.

In the structures of FIGS. 14 through 19, a window 64 is formed centrally in the board wherein two opposite edges have inwardly projecting central bulges or tongues 66. We contemplate that whatever use this structure may have in mounting other circuit elements, it will have particular utility in mounting an entire range of inductors. FIGS. 15 and 16 illustrate the mounting of a high inductance coil '68. The coil consists of a dumbbell shaped core 70, the central portion 72 of less diameter having a winding 74 thereon. The core is contained within a sleeve 76 of ferromagnetic material to complete the magnetic circuit. The sleeve 76 is somewhat longer than the core.

The fit of the core within the sleeve is loose enough so as to permit the winding leads 78 to extend out between one of the dumbbell ends and the inside Wall of the sleeve 76. The assembly is easy and rapid. The wound core is inserted in the sleeve and the sleeve then snapped into the window, the tongues 66 engaging the ends of the sleeve 7 76. The tongues and window generally are fitted to the longitudinal central section of the sleeve so that the sleeve extends out from the mounting board half on one side and half on the other. The tongues 66 extend a short distance into the open ends of the sleeve and bear against the ends of the core to center it longitudinally within the sleeve. Thus a complete mounted coil may be provided by snapping the high inductance coil into the window of the mounting board, the terminal wires being already attached, twisting the coil leads 78 to the short ends of the terminal wires, solder-dipping the short terminal wire ends, dipping the entire mounting board in a Durez dip and baking.

The same general type window may be employed for mounting a low inductance coil as illustrated in FIG. 17 and largely described above. Here, the coil 18 consists of a single layer winding 20 on a tubular cardboard form 22. The coil 18 is snapped into the window so that the tongues 66 extend into the open form ends 86 and support the coil firmly within the window. Again the coil leads are attached to the terminal wires, solder-dipped, and the whole Durez coated.

FIGS. 18 and 19 illustrate the same general concept as applied to a medium inductance coil. Here the coil 88 is a universally wound, washer shaped coil without a core. Again the window 64 is formed .to conform to the cylinder sides or central longitudinal section of the coil, and tongues 66 are provided in the opposite Window sides conforming to the ends of the coil. Again, the coil is snapped into the window so that the tongues 66 extend into the central aperture 92 of the coil 88 to anchor it into the window. The mounted coil is then finished as described.

FIGS. 20 through 23 illustrate another window whereby a variety of circuit elements may be variously contained in a mounting board without the necessity of gluing. In this form, the mounting board is cut centrally across its top and bottom ends as at 94 and a center connecting cut 96 is made between them so as to define a pair of flaps 98. The flaps 98 may be appreciably longer than the coil to be contained. In FIG. 21 is shown a universally wound coil 100 like that in FIG. 19 inserted between the flaps 98 to spring them out so that the flap edges bear against the ends of the coil. The material of the mounting board is stifiiy resilient and will support the coil firmly.

If the lateral extension of the coil of FIG. 21 is not wanted, the flaps 98 can be opened oppositely and the coil 100 inserted between them as particularly illustrated in FIG. '22. The opposite opening of the flaps likewise serves to mount tubular form wound coils 102 as best seen in FIG. 23.

All of these mounting configurations illustrated in FIGS. 14 through 23 possess the advantages, first, of exceedingly quick assembly; second, the use of no glue to retard manufacture and to impair the adhesion of the Durez to the mounting board material; and third, of permitting leakage of the Durez suspension around the coil or circuit element between opposite sides of the mounting board to integrate the Durez coatings on the two sides of the board.

FIGS. 24 and 25 illustrate a method of using the mount of the invention for supporting and connecting a tunable coil. To this end we form a central circular aperture 104 in the center of the mounting board which is smaller in diameter than the coil itself. The edges of the aperture are slit or broken as at 106 to provide a ring of infacing tongues. The coil 108, on a tubular form, may be inserted into the aperture, the tongues holding the coil firmly so as to extend transversely of the mounting board with the bore of the form and consequently the exposed tuning slug 110 readily accessible. If a Durez coating is desired, the core ends may be capped for dipping.

FIGS. 26 and 27 illustrate the use of the coil mount of the invention in a four terminal context. In this situation we provide two coil mounts 111, each having a central bore 112 therein. The coil or transformer 114 proper may be wound on a tubular form 116 having an interior diameter equal to the diameter of the bores 112. The mount-s thus will be butted up against the ends of the form. A tubular sleeve 118 somewhat longer than the form 116 is contained in the form and extends beyond it at either end through and beyond the mounts 111 and is rolled over outwardly at its ends to provide flanges 120 which secure the assembly together. It will be appreciated that since two mounts are employed, there will be four terminal wires thus adapting the structure to such four terminal purposes as the mounting of transformers, etc. The sleeve 118 is open throughout and therefore adapted to receive a metal core or slug if desired.

FIGS. 28 and 29 illustrate a six terminal structure. In this instance, the mount 124 consists of alternating narrow 126 and wide 128 elements connected together but scored as at 129 for folding.

The board can thus be folded into a rectangular configuration as illustrated in FIG. 29, the narrow sections 126 constituting the ends and the wide sections 128 constituting the sides. The narrow sections 126 each have a central terminal Wire 130 mounted therein and the wide or side sections 128 have a pair of spaced terminal wires 131 in the fashion of the simple mounts. The terminal wires may be attached to the mount board in any of the fashions described above, although that method shown in FIG. 7 is illustrated. The six terminal element 132, possibly in the form of a universally wound coil, will be glued to one of the wide members of the mount and the other sides folded thereabout. The opposite wide side should also have adhesive applied thereto in order to maintain the shape of the folded mount and further support the element.

It will be appreciated here that while the windowed mounting boards illustrated in FIGS. 14 through 25 have definite advantages in the speed and inexpensiveness of assembly, there may be instances where the additional expense and time consumption of the gluing operation are justified. It is not our intention, therefore, to exclude necessarily a glued attachment of the circuit element to any of the board structures illustrated in FIGS. '1 through '8, although for most purposes the windowed structures will be preferred.

FIG. 30 illustrates a coil mount 132 of the invention serving also as a form for a low inductance coil. Here the mounting board 134 is formed to be generally rectangular with shoulders 136 extending above and below the board on each side thereof. The terminal wires 138 will be centered in the shoulders. Thereafter the appropriate number of turns of coil Wire 140 are wrapped around the central portion of the mounting board between the shoulders 136 and secured to the short terminal wire ends 142 in the fashion described. The shoulders serve to space the coil wire from the terminal wires and avoid unwanted shorting. The shoulders also define an index to the solder dip and the tinning dip so that the coil wire 140 on the board will not be exposed to solder immersion.

It will be appreciated from the foregoing description of the many modifications of the invention that we have devised a coil mount and a mounted coil suitable for insertion into electric circuits, particularly of the printed circuit kind, which represents a notable advance over anything known in the art. It is simple, inexpensive, occupies little space, and is exceedingly flexible in its application. The speed and ease of manufacture of such circuit components embodying the invention are notable. It will be further appreciated that although we have described several specific embodiments of the invention it is not to be regarded as being limited only to those shown. Others undoubtedly will suggest themselves and we desire,

therefore, that our invention be regarded as being limited only as set forth in the claims hereof.

In the claims, the term untrimmed is used as defining terminal wire lengths. As described above, the staple insertion of the terminal wires into a mounting board limits the ends of the terminal wires to relatively short lengths and demands that they be of equal length. It will be appreciated that an unequal length of leg could be obtained subsequently by cutting one of the legs of each of the staples even shorter. This is, however, wasteful of terminal wire, requires an additional operation, and still does nothing to extend the possible length of the other leg. The legs of the terminal wires of the invention could be defined as long to distinguish over the staple type, and in some instances are, but this is a characterization lacking in definiteness. More definite is the characterization of the terminal wires being unequal initially or without a subsequent trimming or shortening operation.

We claim:

1. A mounted coil which comprises a sheet of stiff, resilient, electrically insulating material, said sheet having a window in the central portion thereof, two opposite edges of said window having bendable, resilient tongues projecting inwardly therefrom, a pair of parallel terminal wires secured adjacent opposite edges of said sheet, said wires projecting beyond the lower edge at least of said sheet, an annular coil contained in said window, said tongues entering the hole of said coil, said coil having leads connected to said terminal wires.

2. The combination as set forth in claim 1 including additionally an encapsulation of rigid insulating material encompassing all of said coil except the lower edges of said wires.

3. A mounted coil comprising a sheet of stifi, resilient, electrically insulating material, a pair of parallel terminal wires secured adjacent opposite edges of said sheet, said wires extending beyond said sheet at at least one end thereof, said sheet being slit between said wires to define a flap resiliently flexible out of the plane of said sheet to define an aperture in said sheet, a coil contained in said aperture by a resilient bearing thereagainst of said flap, said coil having leads secured to said terminal wires.

4. A mounted coil comprising a sheet of stiff, resilient, electrically insulating material and a pair of parallel terminal wires secured adjacent opposite edges of said sheet, said wires extending beyond said sheet at at least one end, said sheet being formed between said wires to provide opposite flaps having facing free edges, a coil resiliently secured to said sheet between said flaps by a resilient bearing thereagainst of said flaps, said coil having leads secured to said wires.

5. A mounted tunable coil comprising a sheet of stiff, resilient, electrically insulating material, a pair of parallel terminal wires secured to said sheet and extending beyond said sheet at at least one end thereof, a coil comprising a tubular form and a winding thereon, said sheet having an aperture therein smaller than thecircular section of said coil and a plurality of infacing flexible tongues surrounding said aperture, said coil being transversely con tained in said aperture by a flexure of said tongues out of the plane of said sheet, said winding having leads connected to said wires, and a tuning slug in said form.

6. A mounted tunable coil comprising a sheet of stiff, resilient, electrically insulating material, a pair of parallel terminal wires secured to said sheet and extending beyond said sheet at at least one end thereof, a generally tubular coil, said sheet having an aperture therein greater than the transverse circular section of said coil, a tongue extending in from the periphery of said aperture, said coil extending transversely into said aperture, said tongue bearing resiliently against the cylindrical surface thereof to retain said coil in said aperture, said coil having leads secured to said wires and a tuning slug adjustably mounted within said coil.

7. The combination as set forth in claim 1 wherein said coil occupies essentially the entire width of said window between said edges.

References Cited UNITED STATES PATENTS 2,945,215 7/1960 Sprude 33665 3,296,362 1/1967 Parry 174-68.5 1,953,035 3/1934 Wyss 336-208 2,903,627 9/1959 McGarvey 317-101 2,868,936 l/1959 Francis 3383 17 2,965,865 12/1960 Zack 336192 2,864,064 12/1958 Heaton 33665 FOREIGN PATENTS 945,704 12/ 1948 France. 945,037 4/ 1947 France.

THOMAS J. KOZMA, Primary Examiner US. Cl. X.R. 

